<!DOCTYPE html>
<html>
<head>
    <title>border-radius</title>
    <style type="text/css">
        div {
            width: 300px;
            height: 300px;
            border: 2px solid #f00;
            border-radius: 100%;
        }
    </style>
</head>
<body>
<div></div>
</body>
</html>
